Senate Minority Leader Chuck Schumer’s bid to continue leading the Democratic Party when it takes control of the US Senate in January continued to falter Monday night as a key machinists’ union asked the New York senator to step aside and allow “a new generation to lead Senate Democrats.”

In a letter, Brian Bryant, international president of the International Association of Machinists and Aerospace Workers (IAM Union) thanked Schumer for “many years of leadership, friendship, and unwavering commitment to working people” before telling him that “after thoughtful discussions,” the IAM Union Executive Council had opted not to support Schumer’s push to remain as the Senate leader.